Special Issue: ‘Advanced Studies in Maintaining Post-Harvest Quality of Fruits and Vegetables’

1. Introduction

The characteristics of taste, flavor, nutrition, and safety in fruits and vegetables during post-harvest, minimal processing, fresh-cutting, fermenting, and processing are critical elements in the storage and sale of products. The growing demand for fruits and vegetables has led to an increasing interest in the study of maintaining their quality, enhancing their safety, and extending their shelf life [1]. However, fruits and vegetables are prone to tissue damage, wound respiration, water loss, transpiration, ethylene production, enzymatic browning, tissue softening, and secondary metabolite production during storage, transportation, and sale along the supply chain [2,3]. Therefore, there is an urgent demand for any new preservation technologies that can maintain the quality of fruits and vegetables [4,5,6,7]. The purpose of this Special Issue, “Advanced Studies in Maintaining Post-harvest Quality of Fruits and Vegetables“, is to present new preservation technologies to resolve some of these concerns, such as physiological and quality changes, the study of preservation technology and its regulation mechanism, metabolomics and microbial interactions, and any other method that might improve the quality and safety of fruits and vegetables. Articles on maintaining the quality and safety of any kind of fruits and vegetables, including post-harvest, minimally processed, fresh-cut, fermented, and processed fruits and vegetables were welcomed for this Special Issue. After a rigorous review, a total of fourteen articles (one review paper and thirteen research papers) were included in this Special Issue, proposing new preservation technology to improve the quality and shelf life of various fresh horticultural products.

2. Overview of Published Articles

2.1. Physical Preservation Technologies

The quality attributes of post-harvest fruits and vegetables include a fresh appearance, firmness, acceptable texture, characteristic flavor, vitamin content, and a sufficient shelf life to meet distribution. The main significant factors influencing the quality of fruits and vegetables are the temperature, the atmosphere, and the storage time. Modified atmosphere packaging is considered an effective technology for extending the shelf life of fruits and vegetables. Da Silva et al. (contribution 1) evaluated the impact of dipping ‘Palmer’ mangoes in 0.1% and 2.5% (w/v) sorbitol solutions and storing the fruit under a controlled atmosphere (CA) without atmosphere modification (21 kPa O₂ + 0.03 kPa CO₂) at 8 °C with 95% relative humidity (RH) or with 5 kPa O₂ + 5 kPa CO₂ at 4 °C/95% RH for 28 days. The result showed sorbitol was effective in minimizing the chilling injury symptoms and did not compromise the fruit quality, especially when it was stored at 4 °C in association with a CA containing 5 kPa O₂ + 5 kPa CO₂. It reduced lipid peroxidation and increased the activities of the superoxide dismutase (SOD) and ascorbate peroxidase (APX) enzymes in the epicarp and mesocarp, providing greater cold tolerance. Thus, this treatment represents a viable alternative for managing chilling injuries in mangoes. Erbas (contribution 2) evaluated the effects of combinations of modified atmosphere packaging and oxalic acid (OA) treatment on the quality and biochemical content changes in rocket (Eruca sativa Mill. cv. Bengi) leaves. The result showed rocket leaves could be stored at 0 °C for 8–9 days with 1 mM OA treatment. Temperature preservation is one of the most common treatments and traditional physical methods to extend the shelf life of fruits and vegetables. Zhao et al. (contribution 3) studied the effect of near-freezing temperature (NFT) on the chilling injury (CI), proline metabolism, and antioxidant capability of peach fruit during storage times. The results showed that the NFT completely inhibited the occurrence of CI in peach fruit. The NFT significantly (p < 0.05) enhanced the activities of the superoxide dismutase, catalase, ascorbate peroxidase, and the 1,1-diphenyl-2-picrylhydrazyl scavenging capacity. The results suggest that NFT storage can improve the chilling tolerance of peach fruit by regulating the antioxidant defense and proline metabolism, which might represent a potential novel method to store fruits and vegetables for longer times. Elataff et al. (contribution 4) evaluated the effect of different storage temperatures and MeJA on the quality of and antioxidants in post-harvest Shine Muscat table grapes. The results indicate MeJA could play a critical role as a stimulator of fruit quality as well as enhance the physicochemical parameters and antioxidant activities for extending the shelf life of grapes during storage. Hu et al. (contribution 5) investigated the effect of the combination of low temperature and different wounding intensities on the quality of fresh-cut pumpkin; the critical indexes involved in reactive oxygen species (ROS) metabolism, the vitamin C–glutathione cycle, phenylpropanoid metabolism, and membrane lipid peroxidation were monitored for pumpkin. The results showed that with the increase in the cutting injury strength, the lightness, whiteness index, respiration rate, ethylene content, lipoxygenase activity, and malondialdehyde content of fresh-cut pumpkin increased, while the hardness, sensory quality, appearance, and total soluble solid content continuously decreased. Lee et al. (contribution 6) evaluated the quality index changes in the green maturity of Jin Huang mangoes with different ethylene and post-ripening treatments and then when stored at different storage periods at 4 °C followed by 6 days at 20 °C. The result showed that the mangoes treated with 500 ppm ethylene were slow to ripen during 4 °C storage, which could be sustainable even under 20 °C storage. The treatment conditions of Jin Huang mango with ethylene ripening for 1 day and post-ripening at 20 °C for 1 day helped extend its shelf life at 20 °C, stocking and minimizing CI and anthracnose, thereby maintaining a certain quality.

2.2. Chemical Preservation Technologies

The use of edible films/coatings alone or in combination with antioxidants has beneficial effects on the quality of fresh-cut fruits and vegetables [8,9,10,11]. Edible films/coatings can offer a possibility to extend the shelf life of fresh-cut produce by providing a semi-permeable barrier to gases and water vapor and, therefore, reduce respiration, enzymatic browning, and water loss. Sarengaowa et al. (contribution 7) evaluated the quality and safety of fresh-cut potatoes with an alginate-based edible coating containing thyme essential oil (AEC-TEO) during a storage period of 16 days at 4 °C. The research showed that AEC-TEO at a 0.05% concentration was the most beneficial for maintaining the quality and inhibiting microorganisms in the fresh-cut potatoes. This represents a potential application prospect for the preservation of fresh-cut potatoes. Li et al. (contribution 8) investigated the effect of solid lipid nanoparticles containing cinnamaldehyde (SLN-CA) on post-harvest strawberry. It showed that SLN-CA treatment can effectively reduce the probability of decay and softening, maintain a high level of SOD activity in cells, and improve the sensory characteristics of strawberries and thereby their shelf life. A recently developed inhibitor of ethylene action, 1-methylcyclopropene (1-MCP), has been shown to be effective in reducing the quality deterioration and in extending the shelf life of fresh-cut fruits. Kou et al. (contribution 9) summarized the latest available information on the effects of ethylene and 1-MCP with respect to enhancing or impairing sweet potato root quality. A better understanding of the influence of ethylene and 1-MCP on root quality parameters will be useful to further explore the role and mechanisms of action of ethylene in regulating the post-harvest storage of sweet potato roots and the contributions to technological development and innovation. Habibi et al. (contribution 10) investigated the effects of glycine betaine (GB) and/or methyl salicylate (MeSA) on the physicochemical changes, the chemical attributes of the juice, and the peel color of ‘Moro’ blood orange at cold quarantine storage (2 °C) for 60 days. It showed the GB and MeSA treatments offer significant advantages in preserving the physicochemical characteristics and chemical attributes of ‘Moro’ blood oranges during cold quarantine storage. These findings underscore the potential of GB and MeSA treatments for maintaining the quality of ‘Moro’ blood oranges during cold quarantine storage, with a noteworthy synergistic effect between MeSA and GB in preserving the fruit quality.

2.3. Preharvest Treatment Technologies

Preharvest chemical spraying can significantly improve the post-harvest quality of horticultural products. Spraying has a more pronounced effect [12]. Wang et al. (contribution 11) investigated the effects of non-bagging film agents on the contents of the mineral elements and flavonoid metabolites in apple fruits and determined the feasibility of this method. Individual spraying of non-bagging film agents can significantly increase the total contents of mineral elements in apples. Application of plant growth regulators (PGRs) in apricot orchards is a common practice with the goal of improving the yield and/or the quality of fruits at harvest. However, the question of whether such a treatment alters post-harvest properties is seldom answered. Milovic´ et al. (contribution 12) examine the impact of gibberellic acid (GA3) and 6-benzyladenine (BA) on the physical characteristics and composition of apricot fruit after prolonged cold storage (i.e., 21 days) and shelf life. At harvest, significant differences were observed between the treated and untreated fruits regarding the flesh firmness, color, ethylene production and respiration rate, and the flavonoid, carotenoid, and citric acid content, while application of BA100 changed the TA and TSS. There was no difference in the sensory properties of the treated and non-treated fruit after cold storage and in the shelf life.

2.4. Other Technologies

Rodríguez et al., (contribution 13) developed a methodology for evaluating the ripening pattern, internal disorders, flesh composition, and sensory quality of Hass avocados and to determine predictive quality markers to manage these. The research showed the PLS-DA model could be a powerful tool for classifying the internal quality of fruits in avocado-producing countries. Therefore, in countries with highly variable growing conditions and production practices, the use of destructive analyses and multivariate data analyses could reduce the heterogeneity and allow the shipment of fruits with better internal quality to the international market. Tziotzios et al. (contribution 14) investigated the use of a non-destructive hyperspectral imaging approach for the evaluation of kiwifruit cv. “Hayward” internal quality, focusing on physiological traits such as the soluble solid concentration (SSC), dry matter (DM), firmness, and the tannins, widely used as quality attributes. The study concluded that machine learning algorithms, especially neural networks, offer substantial accuracy, surpassing traditional methods for evaluating kiwifruit quality traits. Overall, the current study highlighted the potential of such non-destructive techniques in revolutionizing quality assessment during post-harvest by yielding rapid and reliable predictions regarding the critical quality attributes of fruits.

3. Conclusions

These articles, which are written to a very high standard with excellent citations, were selected from a large number of submissions through rigorous evaluation. This Special Issue strives to promote more in-depth communication among professional and technical personnel in the field of horticultural post-harvest preservation technology, improving post-harvest quality, ensuring product safety, and serving the healthy development of the horticultural industry.